1. Field of the Invention
The present invention relates to an alternator driven by an internal combustion engine which is mounted in a vehicle such as a passenger car, a truck, or boat.
2. Description of the Related Art
It is necessary for an alternator for a vehicle to cool the stator winding, which is a heat source, effectively. JP-A-56-98358 discloses an alternator having a cooling fan inside a frame for sending cooling air directly to the coil ends (hereinafter referred to as the inner fan type) and flat coil ends with increased surfaces to be cooled.
On the other hand, WO92/06527 discloses a stator winding, which is composed of a plurality of conductor segments connected to one another. The above stator winding has gaps between the conductor segments and a more regular pattern of winding than a stator winding composed of a continuously wound wire. Because of the gaps between the coil ends, cooling air can be introduced around the conductor segments easily.
In the inner fan type alternator disclosed in JP-A-56-98358, cooling air is introduced only to the inner side of the coil ends and not to the outer side of the coil ends. In order to provide a reliable performance, an alternator must have expensive conductors coated with heat resistive insulation material. Flat coil ends increase resistance of the air flow, and cooling air is not sufficient to cool the alternator that generates high output power.
In the inner fan type alternator for a vehicle, hot air which has cooled the coil ends is discharged from discharge windows formed in the outer wall of the frame. The temperature of the discharged air becomes higher as the output power of the alternator increases. This affects various parts disposed outside the alternator and can not be ignored in view of the necessary vehicle reliability.
In particular, the non-metal belt on the drive pulley, which is disposed near some of the discharging windows, may be damaged by the hot air in a short period of time. If the belt deteriorates and breaks, the alternator and various engine accessories driven by the belt will stop, causing serious problems.
It is preferable to discharge the hot air from the side opposite to air intake windows in order to cool the coil ends effectively. The above described inner fan type alternator does not have this structure.
In the alternator disclosed in WO92/06527, cooling air is introduced to the conductors disposed at the outer side of the coil ends. Since the discharging direction of the hot air is not taken into consideration in the above prior art, the non-metal belt on the pulley may be damaged.